Contrary to popular belief, neither U.S. Secretary of State John Foster Dulles nor President Dwight D. Eisenhower originated the Domino Theory. Rather, the first American to predict the expansion of Communism across Indochina in the wake of a Communist victory in Vietnam was the American diplomat Charles S. Reed.
In 1946, Reed, (who served as the U.S. Consul in the French colony of Cochinchina), warned officials in the Truman administration that Communist domination of southern Vietnam would almost certainly lead to the spread of Communist influence into neighbouring Laos and Cambodia. There was no mention by Reed of the Communists gaining influence beyond those two countries. Reed’s Domino Theory was limited in geographical scope.
Reed’s theory rested on geographical reality. In the late nineteenth and early twentieth centuries, the French constructed a system of roads, rails, and water routes in Vietnam, Laos, and Cambodia that lay along a west-to-east axis, meaning the commodities of Cambodia and Laos moved east, eventually passing through Vietnam before arriving at the French-built ports strung out along the Vietnamese coastline or at the inland transportation hubs of Saigon, My Tho, and Can Tho.
French Route 9 transported products from Tchepone, Laos, to the port of Tourane (Danang). Route 19 carried commodities from the highlands of Laos and Vietnam down to the coastal port of Qui Nhon. Further south, Route 1 linked central Cambodia to Saigon. International commerce arriving or departing from Phnom Penh’s deep-water port travelled through Vietnam’s Mekong Delta.
Consul Reed understood that Communist control of the Mekong Delta, as well as Vietnam’s harbors, roads, and rails, would translate into Communist influence over Cambodia and Laos. Those two interior nations would be dependent on the Vietnamese for land and water access to the South China Sea and the markets of the world.
Since the French constructed Indochina’s geography to function as a single, interconnected colonial system, it would have been physically- and financially-prohibitive for the people of Laos and Cambodia to decouple from Vietnam and reorient their road, rail, and water transportation systems toward Thailand. Moreover, such a reorientation did not offer the Laotians or Cambodians any guarantee of greater economic and political independence. Shifting transportation routes from a west-east axis to a north-south axis meant Thailand would supplant Vietnam, with the same results for Laos and Cambodia – continued dependence on an outside power for access to world markets.
The first known American articulation of the Domino Theory was an expression of environmental determinism; a Communist Vietnam would lord over Laos and Cambodia not because of Communism but because of geography.
The Domino Theory underwent significant revision between 1946 and 1965. Initially confined to the countries of Indochina, it eventually encompassed all of the nations of Southeast Asia. By the mid-1960s, the theory’s applicability had extended even further afield. President Lyndon B. Johnson promoted the most expansive version of the theory, arguing that the fall of South Vietnam would lead to the collapse of the American position not only across Southeast Asia but throughout the Western Pacific. LBJ went so far as to argue that South Vietnam’s loss would put the Communist’s at Hawaii’s doorstep.
Five U.S. presidents believed in a version of the Domino Theory or recognized its usefulness as a means of garnering domestic support for U.S. military involvement in Vietnam. But in the end, it was Reed’s articulation of the theory that came true. In the aftermath of the Communist victory in South Vietnam in 1975, the Vietnamese Communists, with the help of the old French geographical system, extended their political, economic, and military influence over Laos and Cambodia.